CHAPTER 3: WILLAMETTE BASIN MERCURY TMDL

1 WILLAMETTE BASIN TMDL: MERCURY September 2006 OREGON DEPARTMENT OF ENVIRONMENTAL QUALITY 3-1 CHAPTER 3: WILLAMETTE BASIN MERCURY TMDL TABLE OF CONTENTS OVERVIEW .. 2 MERCURY in the Environment ..7 Summary of MERCURY TMDL Development and Approach ..8 Food Web Biomagnification Model (FWM) ..8 Estimate of Mass Loads and Sources ..9 Ambient MERCURY Monitoring WILLAMETTE MERCURY 12 Sensitive Beneficial Use Identification.

2 12 Water Quality Standard Pollutant and Target Estimates of MERCURY Mass Loads and Sources ..17 Data Review and MERCURY Mass Loads ..19 Source Seasonal Variation and Critical Loading Water Column Guidance Preliminary Estimate of the Necessary Percent Interim Wasteload and Load Allocations ..34 Margin of Safety ..37 Reserve Capacity ..38 Adaptive Management ..38 References ..39 WILLAMETTE BASIN TMDL: MERCURY September 2006 OREGON DEPARTMENT OF ENVIRONMENTAL QUALITY 3-2 OVERVIEW The bioaccumulation of MERCURY in fish is a well recognized environmental problem throughout much of the United States.

3 The number of states that have issued fish consumption advisories pertaining to MERCURY has risen steadily from 27 in 1993 to 45 in 2002 (USEPA, 2003). The Oregon Department of Human Services (DHS) has issued multiple fish consumption advisories for MERCURY in the WILLAMETTE BASIN (DHS, 1993, 1997a, 1997b, 2001, 2004a, 2004b) advising consumers of fish of the health risks associated with eating fish caught from the WILLAMETTE River and the Dorena and Cottage Grove Reservoirs. These fish consumption advisories represent an impairment of the beneficial use of fishing in the WILLAMETTE BASIN and demonstrate that MERCURY is bioaccumulating in fish tissue to levels that adversely affect public health.

4 The TMDL for MERCURY , described below, is designed to restore the beneficial use of fish consumption to the WILLAMETTE River and its tributaries. One of the primary goals of this TMDL is to establish an interim water column guidance value deemed to be protective of the beneficial use of fish consumption in the WILLAMETTE BASIN . This interim guidance value, when attained, should eventually reduce the concentrations of MERCURY in fish tissue to levels that no longer pose an unacceptable health risk to consumers of the fish.

5 This TMDL document describes the methodology utilized in establishing the interim water column guidance value as well as the sector-specific load reductions necessary for the eventual attainment of the guidance value concentration. The corresponding Water Quality Management Plan (WQMP) outlines the implementation strategy that will promote MERCURY reductions throughout the BASIN , the eventual attainment of the established water-column guidance values and, ultimately, the restoration of the beneficial use of fish consumption.

6 The goals and objectives of this TMDL are consistent with the requirements of the federal Clean Water Act, Oregon s Administrative Rules, and ODEQ s MERCURY Reduction Strategy (ODEQ, 2003a). ODEQ acknowledges the current limitations to our understanding of the fate, transport, bioaccumulation, loading and sources of MERCURY in the WILLAMETTE BASIN . These limitations have the potential to influence the estimates of the loading of MERCURY in the WILLAMETTE system, the sector-specific source contributions, the water column guidance values, as well as the estimated reductions necessary to restore the beneficial use of fish consumption.

7 For this reason, ODEQ is establishing interim water column guidance values and sector-specific allocations at this time, based on the collected body of information currently available. The preliminary sector-specific allocations will not be translated into numeric water quality based effluent limits for individual point sources at this time. The interim targets and allocations will be used to define the extent of the problem and to identify the level of effort needed to address the bioaccumulation of MERCURY in fish.

8 ODEQ intends to require specified domestic and industrial point sources in the WILLAMETTE BASIN to monitor their effluent for MERCURY and to submit their data to ODEQ. MERCURY minimization plans will also be required from select sources and sectors. These minimization plans will serve as the primary vehicle for implementing MERCURY reduction activities within the point source sector. Nonpoint sources will also be expected to incorporate MERCURY concerns into the established mechanisms for TMDL implementation pertaining to agriculture, forestry, and urban land use activities.

9 This incremental approach for the MERCURY TMDL is warranted due to the assumptions and limitations of the currently available information. ODEQ believes that the interim approach described in this CHAPTER is consistent with State and Federal law and meets the specific requirements of TMDLs as presented in Table ODEQ plans to develop revised estimates of the water column guidance values and allocations by 2011. At that time, ODEQ will have the opportunity to translate the revised allocations into water quality based effluent limits for wastewater point sources.

10 In the interim, ODEQ will develop a comprehensive conceptual framework for assessing MERCURY behavior in the BASIN , along with the methodological and modeling tools needed to calibrate and validate this framework. To provide data for this purpose, ODEQ will: (1) conduct three years of water quality monitoring to collect additional information on ambient MERCURY and methyl MERCURY concentrations and (2) perform additional source characterization work to help refine the estimates of sector-specific source contributions.